Iris recognition via plenoptic imaging

ABSTRACT

Iris recognition can be accomplished for a wide variety of eye images by using plenoptic imaging. Using plenoptic technology, it is possible to correct focus after image acquisition. One example technology reconstructs images having different focus depths and stitches them together, resulting in a fully focused image, even in an off-angle gaze scenario. Another example technology determines three-dimensional data for an eye and incorporates it into an eye model used for iris recognition processing. Another example technology detects contact lenses. Application of the technologies can result in improved iris recognition under a wide variety of scenarios.

ACKNOWLEDGMENT OF GOVERNMENT SUPPORT

This invention was made with government support under Contract No.DE-AC05-00OR22725 awarded by the U.S. Department of Energy. Thegovernment has certain rights in the invention.

FIELD

The field relates to technologies for improved iris recognition.

BACKGROUND

Iris recognition is an effective way to identify a person conclusively.For example, a camera can take an image of a person's iris and match itagainst a gallery of irises associated with known individuals. Suchidentification techniques can be helpful in a wide variety of securityand other applications.

Iris recognition works well in ideal conditions; however, problems ariseif the images are less than ideal. For example, if an image is takenfrom an off-angle perspective, conventional recognizers have difficulty.In practice, such images can be common, so iris recognition technologyis hampered by such limitations.

Another challenge to ideal conditions is associated with out-of-focusimages.

Still another problem is that contact lenses can interfere with therecognition process.

Thus, although current iris recognition technologies can provide usefulfunctionality, there is room for improvement.

SUMMARY

The Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. The Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

An embodiment can be a method implemented at least in part by acomputing system, the method comprising: receiving a plenoptic off-angleiris image depicting an iris with an off-angle gaze; from the plenopticoff-angle iris image depicting an iris with an off-angle gaze, creatinga plurality of reconstructed images at different synthetic focal depths,wherein the plurality of reconstructed images comprise differentin-focus regions of the iris; and stitching together the differentin-focus regions of the iris from the plurality of reconstructed images,wherein the stitching generates a fully focused image of the iris.

An embodiment can be a method implemented at least in part by acomputing system, the method comprising: receiving a plenoptic irisimage depicting an iris; from the plenoptic iris image depicting aniris, determining a three-dimensional shape of the iris; storing thethree-dimensional shape of the iris; and applying the three-dimensionalshape of the iris as part of iris recognition processing.

An embodiment can be a method implemented at least in part by acomputing system, the method comprising: receiving a plenoptic irisimage depicting an apparent iris; from the plenoptic iris imagedepicting an apparent iris, computing a geometric shape of the apparentiris; storing the geometric shape of the apparent iris; comparing thegeometric shape of the apparent iris against one or more characteristicsof a contact lens; and responsive to determining that the geometricshape of the apparent iris matches the one or more characteristics ofthe contact lens, sending a message to an iris recognition systemindicating that an apparent iris in the plenoptic iris image is coveredby a contact lens

As described herein, a variety of other features and advantages can beincorporated into the technologies as desired.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example system generating a fullyfocused image of an iris from an incoming plenoptic off-angle irisimage.

FIG. 2 is a flowchart of an example method of generating a fully focusedimage of an iris from an incoming plenoptic off-angle iris image.

FIGS. 3A-B are reconstructed images generated from a plenoptic image ofan off-angle iris with different synthetic focus settings.

FIG. 4 is a block diagram of an example scenario involving stitchingtogether synthetic images with different synthetic focus settings.

FIGS. 5A and 5B are eye images showing eyes at different gaze angles.

FIG. 6 is a block diagram of an example system capturingthree-dimensional shape of an iris for iris recognition processing.

FIG. 7 is a flowchart of an example method of capturingthree-dimensional shape of an iris for iris recognition processing.

FIG. 8 is a block diagram of an example system constructing apersonalized eye model for use in iris recognition processing.

FIG. 9 is a flowchart of an example method of constructing apersonalized eye model for use in iris recognition processing.

FIG. 10 is a block diagram of an example system detecting a contact lensin a plenoptic iris image.

FIG. 11 is a flowchart of an example method of detecting an obfuscatingcontact lens in a plenoptic iris image.

FIG. 12 is a block diagram of an example comparison of a contact lensconfiguration with a naked eye configuration.

FIGS. 13A and 13B are block diagrams comparing different plenopticsystems.

FIG. 14 is an illustration of light field sampling with two-pixelangular sampling.

FIG. 15 is a block diagram of an example system implementing frontalview reconstruction via an eye model.

FIG. 16 is a flowchart of an example method of implementing frontal viewreconstruction via an eye model.

FIG. 17 is a block diagram of an example system constructing areconstructed synthetic eye from an off-angle image.

FIG. 18 is a flowchart of an example method of constructing a syntheticeye from an off-angle image.

FIG. 19 is a block diagram of an example system reconstructing an imagefrom a synthetic eye.

FIG. 20 is a block diagram showing a ray trace model for reconstructinga frontal view.

FIG. 21 is a block diagram showing effects of the limbus.

FIG. 22 is a block diagram showing effect of the limbus on areconstructed frontal image.

FIGS. 23A-B are illustrations of the limbus.

FIG. 24A-C are a rendering of an eye model at 0 degrees and unwrappingresults.

FIG. 25 is a diagram of an example computing system in which describedembodiments can be implemented.

FIG. 26 is an example cloud-support environment that can be used inconjunction with the technologies described herein.

DETAILED DESCRIPTION Example 1 Example Overview

The technologies described herein can be used for improved irisrecognition, such as in scenarios involving images having an off-anglegaze. Adoption of the technologies can provide greatly improvedrecognition, even under less than ideal conditions.

Other aspects relate to three-dimensional eye modeling. A personalizedeye model can be developed via three-dimensional feature extraction.Other aspects relate to contact lens detection.

The technologies can be helpful for those wishing to improve existingsystems by leveraging existing iris image galleries. For example, thetechnologies can serve as a preprocessor for conventional irisrecognition software.

The three-dimensional modeling technologies can implement a personalizedeye model to improve iris recognition.

The contact lens detection technologies can be used to detect thepresence of obfuscating contact lenses, including those that potentiallyinterfere with iris recognition technologies.

Beneficiaries include iris recognition technologists who wish to improverecognition performance under real world conditions. End users alsobenefit from the technologies because they can enjoy better recognitionperformance.

Many of the technologies described herein can be used in conjunctionwith conventional iris recognition technologies, images, and hardwarewith minimal or no modification. Thus, current images and recognitiontechniques can be used without having to retool underlying softwaresystems.

Example 2 Example System Generating Fully Focused Image of an Iris

FIG. 1 is a block diagram of an example system 100 generating a fullyfocused image 180 of an iris from an incoming plenoptic off-angle irisimage 110 as described herein. For purposes of context, an irisrecognition engine 190 is shown. In the example, a fully focused imagestitching engine 150 accepts an incoming set of reconstructed images120A-N and generates a fully focused image 180.

As described herein, the incoming plenoptic off-angle iris image 110 candepict (e.g., capture a scene including) an iris with an off-angle gaze.In practice, other parts of the eye are typically included. Thereconstructed images 120A-N can depict the same iris at differentsynthetic focus planes.

Different synthetic focus settings can be chosen for the differentreconstructed images 120A-N so that different, respective in-focusregions 125A-N are in focus. Due to the off-angle gaze of the iris, thefocus settings typically specify a synthetic focus plane that progressesaway or toward the capture point while moving across the eye.

A reconstructed image 120A can thus be generated from the plenoptic irisimage 110 by applying the synthetic focus plane to the plenoptic irisimage 110. In practice, thresholds can be set to determine how manyreconstructed images are appropriate, or a fixed number can be used. Theshape of the reconstructed images can be blocks, strips, or othergeometric shapes that are typically adjacent to cover the entire iris.

A fully focused image stitching engine 150 can be configured to acceptthe plurality of reconstructed images 120A-N (e.g., at differentsynthetic focus depths) of an iris with an off-angle gaze and output thefully focused image 180. The engine 150 can stitch together differentin-focus regions 125A-N of the iris from the plurality of reconstructedimages 120A-N.

The fully focused image 180 can then be used as part of iris recognitionprocessing done by an iris recognition engine 190.

As part of processing, transforming, masking, machine learning, or othertechniques can be applied to the images to account for the off-anglegaze as described in U.S. Pat. No. 8,958,608 to Santos-Villalobos etal., which is hereby incorporated herein by reference. For example, areconstructed frontal view can be generated for purposes of recognition.Such a reconstructed frontal view process can take the fully focusedimage as input.

The system 100 can be described as a single, unified system, or one ormore client systems and one or more server systems. For example, thestitching engine 150 and iris recognition engine 190 can be considered asingle system or be provided separately by different vendors or parties(e.g., the stitching engine 150 can be a plug-in or preprocessor for theiris recognition engine 190).

In practice, the systems shown herein, such as system 100 can vary incomplexity, with different functionality, components of differingcomplexity, and the like. For example, additional preprocessing orpost-processing can be performed on the images 110, 120A-N, 180.Additional functionality related to iris recognition (e.g., security,biometrics, or the like) can also be incorporated.

The system 100 and any of the other systems described herein can beimplemented in conjunction with any of the hardware components describedherein, such as the computing systems described below (e.g., one or morehardware processing units, computer-readable memory coupled to theprocessing units, and the like). In any of the examples herein, theinputs, outputs, images, regions, models, and engines can be stored inone or more computer-readable storage media or computer-readable storagedevices. The technologies described herein can be generic to thespecifics of operating systems or hardware and can be applied in anyvariety of environments to take advantage of the described features.

Client/server operation can be supported, and cloud computing techniquescan be applied to give clients the ability to perform the describedtechniques via a local application without concern over the actualcomputing infrastructure needed or used to operate the servers, whichcan be administered by a business entity different from the client userorganization.

Example 3 Example Method Generating Fully Focused Image

FIG. 2 is a flowchart of an example method 200 of generating a fullyfocused image of an iris from an incoming plenoptic off-angle iris imageand can be implemented, for example, in the system shown in FIG. 1.

At 210, an incoming off-angle iris plenoptic image depicting an iriswith an off-angle gaze is received. For example, a plenoptic camera canbe used to capture a plenoptic image of a subject's eye.

At 220, from the off-angle iris image, a plurality of reconstructedimages are generated from the plenoptic image. As described herein, avariety of techniques can be used to generate the reconstructed imagesso that they comprise different in-focus regions of the iris. Forexample, the reconstructed images can be at different synthetic focusdepths. As described herein, the reconstructing can account for theoff-angle gaze so that the reconstructed images comprise in-focusregions covering the entire iris.

An iris correlation filter can be applied to reconstruct images atdifferent planes to identify the iris object within respective of theplanes. Sharpness can then be measured for the planes (e.g., via an edgefilter such as a Sobel edge detector operator or the like). If the irisis in focus for a given plane, the sharpness measurement is high (e.g.,relative to other planes or exceeding a threshold), while forout-of-focus, the sharpness measurement is low. The iris regions withthe highest sharpness or those exceeding a threshold can be selected forstitching.

Accordingly, the incoming image can be divided into overall regions, andin-focus regions of reconstructed images (e.g., from the reconstructedplanar image for which the region is in focus) can be chosen based onthe overall regions as described herein.

At 230, a fully focused image of the iris is generated. Such generationcan comprise stitching together the different in-focus regions fromrespective of the reconstructed images.

In practice, the reconstructed image is then used for iris recognitionpurposes. At 240, the fully focused image of the iris is output. Theimage can then be used for iris recognition purposes (e.g., submitted toan iris recognizer or iris recognition software for iris recognitionprocessing) as described herein. Techniques such as transforming,modeling, masking, machine learning, and the like can be applied asdescribed in U.S. Pat. No. 8,958,608 to Santos-Villalobos et al.

The method 200 and any of the other methods described herein can beperformed by computer-executable instructions (e.g., causing a computingsystem to perform the method) stored in one or more computer-readablemedia (e.g., storage or other tangible media) or stored in one or morecomputer-readable storage devices.

Example 4 Example Plenoptic Camera

In any of the examples herein, a plenoptic camera (sometimes called a“light-field camera”) can capture a variety of information about ascene. A characteristic of plenoptic image data is that the image can berefocused after the image is captured.

Depth information can also be obtained from the plenoptic image data.

The actual hardware used to capture a plenoptic image data can vary. Asingle camera can be used, but a plenoptic camera system can use aplurality of cameras (e.g., microcameras or the like). Other techniques,such as optical heterodyning and the like can employed to implement aplenoptic camera.

Example 5 Example Iris Recognition Processing

In any of the examples herein, iris recognition processing can include awide variety of processing including enrollment of subjects (e.g.,adding their information to a gallery), verification (e.g., verifyingthat a subject matches information for an enrolled subject oridentifying an unknown subject), and the like. Iris recognitionprocessing can also take the form of determining whether or not asubject is wearing a contact lens.

In practice, an output indicates the results of processing, such as anidentity (e.g., as determined from matching a gallery), a match, orwhether the subject is wearing a contact lens.

Processing can include off-angle gaze processing (e.g., correcting theimage, transforming the image, applying an eye model, or the like).

Example 6 Example Plenoptic Iris Image

In any of the examples herein, a plenoptic iris image can be an image ofan iris captured by a plenoptic camera. Such an image is sometimescalled a “light field,” and can serve as the source image data fromwhich reconstructed images can be generated. For example, syntheticimages of different focus depths can be generated as described herein.

The image can also include depth data or raw data from which depth datacan be calculated. The plenoptic image can be stored in a data structurethat allows additional data, such as depth data, to be aggregated intothe record as processing progresses.

Example 7 Example Fully Focused Image

In any of the examples herein, an image can be constructed with aplurality of synthetic focus settings. Such an image is sometimes calleda “fully focused” image. However, the entire image need not be perfectlyin focus. Instead, the image serves as an improvement over an imagehaving only a single synthetic focus setting or an image captured by aconventional camera.

The fully focused image is synthetic in that it does not exist in animage having a single focus setting. Instead, it is a mosaic ofdifferent synthetic images that are themselves synthetically generatedfrom the plenoptic image.

Example 8 Example Synthetic Focus Settings

In any of the examples herein, a synthetic focus setting can take avariety of forms. For example, a synthetic focus plane can be specifiedfor a plenoptic image, and the resulting image will appear as if thefocus setting were set at the focus plane.

As described herein, different images can be generated or reconstructedfrom the same input plenoptic image by specifying different syntheticfocus planes for respective of the images (e.g., each reconstructedimage has a different synthetic focus plane).

Example 9 Example Identification of in-Focus Regions or in-Focus Images

In any of the examples herein, focus can be measured via the amount ofentropy in the image, the frequency response of the lines in the images,the contrast between neighboring pixels, or the like. Thus, in-focusregions of an image can be identified using such techniques. Similarly,the focus depth for a reconstructed image (e.g., sharp image) can bechosen using such techniques.

Example 10 Example Plenoptic Imaging for Iris Recognition

In any of the examples herein, iris recognition can benefit fromplenoptic technology in that the iris can be imaged without concern offocus (e.g., at the time the image is captured). If the iris plane isoutside the default focus plane, then the system can search for adifferent synthetic focus plane in the light field that produces a sharpiris image.

Another challenge in iris recognition is off-angle iris recognition.Given the fixed and short focal length of most iris scanners, theirdepth of field is too shallow to have an off-angle iris image fully infocus. Light field synthetic reconstructions of an off-angle iris mayhave the same problem, but because one can shift the depth of focus, onecan reconstruct the iris at different depths. For each reconstructeddepth, there can be a corresponding iris image with some regions infocus and other regions out of focus. The region in focus can bedetermined with the techniques described herein (e.g., entropy and thelike).

Then, as shown in FIG. 4, in-focus regions can be stitched together inorder to generate a fully focused off-angle iris image. Severalpartially focused iris images (e.g., the in-focus regions therein) canbe stitched together to form a fully focused iris image.

Example 11 Example Reconstructed Images

In any of the examples herein, reconstructed images can be generatedfrom an incoming plenoptic image. For example, reconstructed images cancontain different in-focus regions (e.g., different parts of the irisare in-focus). The in-focus regions can then be stitched together asdescribed herein.

FIGS. 3A-B are reconstructed images generated from a plenoptic image ofan off-angle iris with different synthetic focus settings. The imageswere reconstructed by specifying different synthetic focus depths for asame plenoptic image captured with a Lytro camera available from Lytro,Inc. of www.lytro.com. In the example of 3A, the eyebrows 310 are infocus. In the example of 3B, a portion 320 of the iris 320 is in focus.

A reconstructed image can be divided into a plurality of regions. Atleast one of the regions can be determined as being in focus. Thein-focus region can then be used for the stitching together as describedherein.

In practice, the plenoptic off-angle iris image can be divided into aplurality of overall regions. Respective of the reconstructed images canbe identified as having in-focus regions corresponding to the overallregions. Stitching together can then stitch together the in-focusregions corresponding to the overall regions.

Another way to achieve generation of a fully focused image is toidentify the in-focus regions in respective of the reconstructed imagesand then stitching them together as described herein.

FIG. 4 is a block diagram of an example scenario 400 involving stitchingtogether reconstructed images 410A-N with different synthetic focussettings. In the example, the reconstructed images 410A-N are generatedby applying different synthetic focus planes to the plenoptic image.

The resulting reconstructed images 410A-N contain in-focus 430 andout-of-focus 440 regions. The in-focus regions 430 are stitched togetherto yield the fully focused image 420. Although the example showsreconstructing an entire area of an image, in practice, only part of theimage need be reconstructed (e.g., the area that contains the iris andpossibly some neighboring area).

Example 12 Example Off-Angle Gaze

In any of the examples herein, an off-angle gaze can denote an eye oriris with a gaze angle other than that from a frontal perspective. Forpurposes of convenience, a completely frontal view (e.g., a gaze in linewith the optical axis) can be denoted as 0 degrees or “on-axis.”Off-angle gazes involve perspectives taken from off angles, where theangles are deviated from 0 degrees in a horizontal plane, a verticalplane, or both. For purposes of convenience, such angles are designatedas θ_(v) for vertical gaze angles and θ_(h) for horizontal gaze angles(e.g., azimuth). In practice, a particular off-angle gaze may have oneor both of vertical and horizontal components, and the technologiesdescribed herein can be applied to such scenarios. Some examples hereinrefer to a gaze angle without specifying horizontal or vertical; suchangles are typically assumed to be θ_(h).

FIGS. 5A-B are eye images showing eyes at different gaze angles. Theimage of 5A comprises an on-axis (0 degrees) iris image, and the imageof 5B comprises a 40 degree off-axis iris image. For an on-axis image,the eye and camera share the same optical axis, while for off-axisimages, the axes have different directions. Technologies such as thosedescribed in U.S. Pat. No. 8,958,608 to Santos-Villalobos et al. canreconstruct (e.g., estimate) the image of 5A based on an input imageresembling that of 5B.

Although the term “gaze” is used, the direction in which the eye isgazing (e.g., with respect to the gazer) can be independent of the gazeangle. For example, an iris image of a frontally gazing eye can becaptured at a 30 degree angle, resulting in a 30 degree gaze angle.Thus, the term “gaze” can be used to denote the angle at which the eyeis gazing with respect to the capture perspective.

The term “off-angle” can be used to denote an image or otherrepresentation of an eye or iris that exhibits an off-angle gaze. Asdescribed herein, the gaze angle can be at or more than 30, 40, 50, 60,or 70 degrees away from frontal.

Example 13 Example Capture of Three-Dimensional Information

FIG. 6 is a block diagram of an example system 600 capturingthree-dimensional shape of an iris 662 for iris recognition processing.In any of the examples herein, such a shape can be used in apersonalized eye model for iris recognition processing.

In the example, a three-dimensional iris generation engine 650 accepts aplenoptic iris image 610 (e.g., an image of an iris captured by aplenoptic camera). The engine 650 can be configured to generate athree-dimensional shape 662 of the iris depicted in the image 610.

The three-dimensional shape of the iris 662 can be superior to theplanar shape that would ordinarily be used in the alternative. Further,because eye geometry can vary from subject to subject, capturing theactual three-dimensional shape of the eye can lead to superior resultswhen compared to a generic eye model. Eye models based on such capturedthree-dimensional information are sometimes called “personalized” eyemodels herein.

The three-dimensional shape of the iris 662 can be integrated into irisrecognition processing 680, whether enrollment, verification, or both.For example, the shape 662 can be incorporated into a personalized eyemodel as described herein.

Example 14 Example Method Capturing Three-Dimensional Shape of an Iris

FIG. 7 is a flowchart of an example method 700 of capturingthree-dimensional shape of an iris for iris recognition processing andcan be implemented, for example, via the system shown in FIG. 6.

At 710, a plenoptic image of an iris is received. For example, aplenoptic image of a subject's eye can be received.

At 720, the three-dimensional shape of the iris is determined. Forexample, a depth map of the image (e.g., the eye, iris, or the like) canbe computed via the plenoptic image. The iris as depicted in the imagecan be segmented. Thus, the area of the image comprising the iris can becomputed (e.g., via segmentation). The segmented iris can then beregistered to the depth map so that the relative depths at points withinthe iris can be calculated. The image can be rotated if it is off-angle.

At 730, the three-dimensional shape of the iris is stored. For example,a format accommodating iris shapes can be used.

At 740, the three-dimensional shape is applied as part of irisrecognition processing, whether enrollment, verification, or both. Suchprocessing can include constructing a personalized eye model based onthe three-dimensional shape of the iris, and iris recognition can beperformed via the personalized eye model. For example, via the via thepersonalized eye model, a frontal view of an iris depicted in anoff-angle iris image (e.g., the image used to construct the personalizedeye model or some other image) can be reconstructed. Iris recognitioncan then be performed with the reconstructed frontal view.

From the plenoptic iris image, a three-dimensional shape of a limbusdepicted in the plenoptic iris image can also be determined. Thethree-dimensional shape of the limbus can be stored, and it can beapplied during iris recognition processing. For example, irisrecognition can account for the three-dimensional shape of the limbus.

In cases where the plenoptic iris image depicts an iris with anoff-angle gaze, a portion of the iris that is occluded by the limbus inan on-angle gaze can be determined based on the three-dimensional shapeof the limbus. During iris recognition, the occluded portion can beremoved from consideration (e.g., during segmentation).

Three-dimensional positional information of the iris and limbus can alsobe stored as described herein. In an off-angle gaze scenario, a portionof the iris that is occluded by the limbus in an on-angle gaze can bedetermined based on the three-dimensional position of the limbus. Duringiris recognition, the occluded portion can be removed from consideration(e.g., during segmentation).

Example 15 Example Three-Dimensional and Shape Information

In any of the examples herein, three-dimensional and shape informationcan be stored in a variety of ways. For example, the three-dimensionalinformation can be represented as a depth look up table that is used toassociate pixel coordinates (e.g., in x, y space) with a depth ordistance representing z as determined via the techniques describedherein.

The three-dimensional coordinates of certain eye structures, such as thelimbus ellipse, pupil ellipse, and specular highlights on the cornea canbe used to estimate the position and angle of the eye relative to thecamera as well as to estimate the three-dimensional shapes of suchstructures.

Such a representation can be used to create an optical model of the eye,where the iris is represented as a height field, and the limbus andcornea are represented using constructive geometry using primarilyplanes and ellipsoids.

The combined representation can serve as a personalized eye model thatcan be used with ray tracing technologies to recreate undistortedimages.

Example 16 Example System Constructing Personalized Eye Model

FIG. 8 is a block diagram of an example system 800 constructing apersonalized eye model for use in iris recognition processing. Thesystem 800 operates to generate a personalized eye model 860 that can beused in conjunction with other systems to provide iris recognitionprocessing.

In the example, an incoming plenoptic iris image 810 is processed by athree-dimensional eye component generation engine 850, which generatescomponents of a personalized eye model 860. For example, thethree-dimensional shape of an iris 862 can be generated as describedherein. The three-dimensional shape of the limbus 864 can also begenerated, along with transparency, thickness, and height of the limbusdepicted in the image 810. Three-dimensional positional information 866can indicate the position of the various components of the model 860. Inpractice, the position can be relative (e.g., a component's position isindicated relative to a reference point or another component).

In practice, the personalized eye model 860 can comprise additionalinformation.

As shown, the personalized eye model 860 can then be applied to irisrecognition processing, whether enrollment, verification, or both. Forexample, the shape of eye components can be used to better achieverecognition.

A typical iris recognition system assumes that the eye is lookingdirectly at the camera when photographed. Such systems are incapable ofcorrecting the distortions to the iris shape introduced (e.g., by thecornea) when the iris is imaged from off-angle. The personalized eyemodel can serve as a custom optical model for an image and allows theiris to be rendered as if the image were taken in a frontal orientationto allow the matching software to accurately identify the iris.

Example 17 Example Method of Constructing Personalized Eye Model

FIG. 9 is a flowchart of an example method 900 of constructing apersonalized eye model for use in iris recognition processing and can beimplemented, for example, in a system such as that shown in FIG. 8.

At 910, a plenoptic image depicting an iris is received.

At 920, the three-dimensional shape of eye components is determined. Asdescribed herein, such eye components can comprise the iris, limbus, andthe like.

At 930, the three-dimensional shape of the eye components is stored in apersonalized eye model.

At 940, the personalized eye model is applied as part of irisrecognition processing (e.g., enrollment, verification, or both).

Example 18 Example Eye Model

In any of the examples herein, an eye model can be used to model thebiology and anatomy of an eye when performing analysis on images orgenerating precomputed transformations that are subsequently used aspart of iris recognition processing. As described herein, the model canbe anatomically based. An aspherical eye model can be used. Theaspherical shape can be symmetrical (e.g., near-sphere, ellipse) orasymmetrical (e.g., melon shape). The aspheric shape can be corrected toaccount for defects such as astigmatism. Components (e.g., structures)within the eye, such as the limbus, cornea, aqueous humor, and the irisitself can be modeled via the model. The elements of the model can begrouped conceptually even if stored separately.

In practice, the eye model is a collection of digital parameters thatcan model three-dimensional or two-dimensional structures, account foran index of refraction, the position of structures within the eye, thegaze angle, and the like.

In the example, the model can include aspherical dimensions as describedherein, aqueous humor characteristics, iris characteristics, and corneacharacteristics.

Limbus effect logic can simulate the effects of occlusion by the limbusand can include physical characteristics of the limbus.

Although a generalized eye model can be used with success, apersonalized eye model can be used to model individuals, subpopulations,or the like. As described herein, the eye model can be personalized byacquiring three-dimensional shape information about eye components andstoring them as part of the eye model when performing iris recognition.

Example 19 Example Reconstructed Synthetic Eye

In any of the examples herein, a synthetic eye can be constructed foruse in reconstructing a frontal view. In practice, an off-angle imagecan be used to construct the synthetic eye (e.g., the iris). A digitalrepresentation (e.g., map) of the iris can thus be stored.

Subsequently, a simulated frontal view of the synthetic iris (e.g., witha synthetic camera) can be used to reconstruct a frontal view of theiris portrayed in the off-angle image. Corneal refraction, limbuseffect, and other effects can be modeled because actual (e.g.,non-reconstructed) frontal images involve such effects.

Example 20 Example Three-Dimensional Feature Extraction

In any of the examples herein, three-dimensional feature extraction canbe performed. The capture of off-axis irises is a challenge due to theshallow depth of field of most near-field imaging systems. However, theoff-axis iris is also affected by perspective deformation and opticaldeformation. The former is a consequence of a slant view of the eye;while the latter is due to the refraction of light rays at the cornealinterface.

A model-based technology can be used to transform the off-axis iris toits frontal view as described in U.S. Pat. No. 8,958,608 toSantos-Villalobos et al. A generalized eye model and camera model can beused to trace light rays from an off-axis iris image to the eye modeliris plane, and finally to the image plane of an on-axis positionedcamera (e.g., as shown in FIG. 20). Then, the on-axis projection of theoff-axis iris is used for recognition. The model-based technologies canaddress perspective and cornea refraction deformations.

Such a model-based method can yield superior results. However, theaccuracy of the model can be improved. If the model-based technologymodels the iris as planar, it is somewhat inaccurate because the irissurface is irregular and varies by approximately 0.5 mm. In addition,the size of the limbus cannot be correlated to the size of any other eyecomponent. Because the limbus can be important for iris segmentation, ageneralized model-based technology may not work for a large set ofsubjects, given that the geometry of the eye varies significantly fromperson to person.

Improved off-axis iris recognition can be achieved by generating aperson-specific eye model for a subject enrolled in an iris gallery(e.g., for a plurality of enrolled subjects, the subjects have arespective personalized eye models). The eye model can be personalizedby estimating the shape of a subject's eye components with a plenopticcamera. One can replace the planar iris with an irregularthree-dimensional surface of a person-specific iris, the limbus with itsactual transparency, thickness, and height, and the position of the eyecomponents. The three-dimensional shape of the iris and limbus can beestimated from the light field captured with a plenoptic camera.

The plenoptic camera can capture slightly different perspectives of theeye. A depth map of the eye can be computed using shape-from-stereo andshape-from-shading techniques. The eye components can be segmented andregistered to the depth map in order to estimate the geometry of the eyecomponents. Consequently, the eye model can be personalized for thesubject by replacing the generalized limbus model and generalized irismodel with the estimated components.

The estimation of the limbus and iris components can be used to feedexisting iris segmentation algorithms. In particular, for off-axis eyeimages, the limbus occludes part of the iris, commonly leading toincorrect iris segmentation. By estimating the three-dimensional shapeand position of the limbus, the occluded area can be correctlyidentified, which can result in a more correct segmentation of the iris.As a consequence of better iris segmentation, recognition of off-axisirises is improved.

Example 21 Example System Detecting an Obfuscating Contact Lens

FIG. 10 is a block diagram of an example system 1000 detecting a contactlens in a plenoptic iris image (e.g., light field). In the example, theplenoptic iris image 1010 may involve an iris that is covered by acontact lens. Such coverage can be physical, optical, or both, and thecoverage may be partial or complete. Thus the image 1010 can depict anapparent iris, whether or not the iris of the subject is actuallyvisible.

A three-dimensional iris generation engine 1050 can generate a geometricshape of the apparent iris based on the plenoptic iris image 1010. Forexample, a depth map can be generated as described herein.

A contact lens detection engine 1070 can analyze the geometric shape1062 with respect to one or more contact lens characteristics 1075(e.g., the shape of a contact lens) and output a contact lens detectionresult 1080.

Example 22 Example Method of Detecting Contact Lens

FIG. 11 is a flowchart of an example method 1100 of detecting anobfuscating contact lens in a plenoptic iris image and can beimplemented, for example, in the system shown in FIG. 10.

At 1110, a plenoptic image of an apparent iris is received.

At 1120, the geometric shape of the apparent iris is determined based onthe plenoptic image. For example, a depth map can be used as describedherein.

At 1130, the geometric shape of the apparent iris is stored.

At 1140, the geometric shape of the apparent iris is compared againstone or more characteristics of a contact lens. For example, the shape(e.g., curvature) of the iris can be compared against a threshold. Aconfidence score can also be generated.

A common technique for defeating iris biometrics is to wear a contactlens with a false iris texture printed on the surface. Such lenses arecommonly used for cosmetic purposes for changing eye color, but they canbe inadvertently or intentionally interfere with the iris recognitionprocess. If such an obfuscating contact lens is present, the depth mapwill indicate that the iris pattern is placed on the surface of thecornea. The obfuscating contact lens can be distinguished from a depthmap where the iris is imaged through the optics of the cornea.

Eccentricity can be used to represent curvature and thus shape. Thecurvature of the iris texture can be estimated by fitting an ellipsoidsurface to the portions of the depth map corresponding to the iris, andthe eccentricity of the ellipsoid indicates if an obfuscating lens ispresent.

When the characteristics comprise a threshold curvature, the curvatureof the shape of the apparent iris can be compared against the thresholdcurvature.

At 1150, if there is a match between the image and the characteristics,a contact lens is indicated, so a message indicating presence of thecontact lens can be sent.

Example 23 Example Geometric Shape

In any of the examples herein, the geometric shape of an apparent iriscan be generated from a plenoptic image. In practice, the shape is athree-dimensional shape. However, it can be represented as atwo-dimensional geometry (e.g., a plane or a dome) that is atwo-dimensional slice of the actual three-dimensional shape.

Example 24 Example Contact Lens

In any of the examples herein, a contact lens can include cosmeticcontact lenses, colored contact lenses, printed contact lenses, or thelike. In some cases, a contact lens can cover or otherwise distort theiris, and is therefore sometimes called an “obfuscating contact lens.”For convenience, such lenses are sometimes called “printing patterns”contact lenses. The plenoptic image can include optical depthinformation for such lenses, allowing their detection as describedherein.

FIG. 12 is a block diagram 1200 of an example comparison of anobfuscating contact lens configuration with a genuine irisconfiguration. Geometry estimation of eye components where a subject iswearing a contact lens with printing patterns (left) and no contact lenswith printing patterns (right) are shown. Depth information can beobtained as shown.

As can be seen, shape information will differ dramatically in the twoconfigurations. The limbus can also be taken into account when detectingthe contact lens.

Example 25 Example Contact Lens Detection Result

In any of the examples herein, a contact lens detection result canindicate the results of detecting an obfuscating contact lens. Forexample, the result can simply indicate a yes/no (e.g., Boolean) result,a confidence score (e.g., 95% confident), or both (e.g., 95% confidentno contact lens). In practice, a message can be sent to an irisrecognition system indicating that an apparent iris in the image iscovered by a contact lens. In practice, such a message can be acceptedby iris recognition software and an appropriate warning displayedresponsive thereto (e.g., “the subject is wearing a contact lens,”“remove contact lens,” etc.).

Example 26 Example Combination of Obfuscating Contact Lens Detectionwith Three-Dimensional Feature Extraction

In any of the examples involving three-dimensional feature extraction,obfuscating contact lens detection can be incorporated. For example,based on the three-dimensional shape of the iris, it can be determinedthat no obfuscating contact lens is present. Responsive to suchdetermination, iris recognition processing can continue.

Example 27 Example Detection of Printing Pattern Contacts

In any of the examples herein, a contact lens with printing patterns canocclude the underlying iris pattern. Consequently, a subject is toremove such devices before being imaged by the iris recognition systemto avoid inaccurate results. Consequently, it is desirable for the irisrecognition system to detect the use of such contact lenses.

As described above, the geometry of the eye can be estimated from thelight field of a plenoptic camera. If a subject is wearing a contactlens with printing patterns, the estimated iris will appear as a dome,while an iris seen through the transparent cornea should have a shapemore similar to a plane. Consequently, by analyzing the shape of theestimated iris geometry, one can detect if the subject is wearing acontact lens that may be changing the underlying pattern of the iris.

A contact lens detection result can indicate the results of detecting anobfuscating contact lens. For example, the result can simply indicate ayes/no (e.g., Boolean) result, a confidence score (e.g., 95% confident),or both (e.g., 95% confident no contact lens). In practice, a messagecan be sent to an iris recognition system indicating that an apparentiris in the image is covered by a contact lens. In practice, such amessage can be accepted by iris recognition software and an appropriatewarning displayed responsive thereto (e.g., “the subject is wearing acontact lens,” “remove contact lens,” etc.).

Example 28 Example Preprocessing Before Recognition

In any of the examples herein, the resulting image can be used in apreprocessing scenario. For example, the stitching, reconstructing,three-dimensional modeling or other processing can be performed as imagepreprocessing before submission to iris recognition logic or software.The iris recognition software can be provided by a third party. Thepreprocessing can be performed by a plug-in or other extension to theiris recognition software or be fully integrated therein.

Submission of the resulting image to iris recognition software canresult in superior iris recognition performance, even at large gazeangles.

Example 29 Example Light Spectra

In any of the examples herein, processing can be performed on a varietyof light spectra. For example, visible light can be used, but infra-redand ultraviolet wavelengths can also be included or used in thealternative.

Example 30 Example Plenoptic Systems

FIGS. 13A and 13B are block diagrams comparing different plenopticsystems 1310 and 1360. In the examples, the systems 1310, 1360 generateimages that can be processed by an iris recognition processor thatperforms iris recognition processing 1320, 1370 as described herein.

A conventional camera is composed of a main lens and a photon detector.The main lens of a camera is typically a system of lenses thatcorrective optical aberrations and focus photons to an image plane. Onthe other hand, the plenoptic camera integrates a microlens array to theimaging system. As shown in FIGS. 13A and 13B, there are two mainconfigurations for a plenoptic camera. FIG. 13A illustrates the designof the original plenoptic camera (“plenoptic 1.0”). The system 1310 hascomponents A1, A2, and A3, which are the detector, microlens array, andmain lens, respectively. FIG. 13B illustrates the design of the focusedplenoptic camera (“plenoptic 2.0”). The system has components B1, B2,B3, and B4, which are the detector, microlens array, virtual image plane(focal plane for main lens), and the main lens, respectively. Additionalconfigurations can be implemented.

For both designs, the microlens array is placed between the main lensand the detector. For plenoptic 1.0, the main lens reproduces the objectat the microlens array plane, while for the plenoptic 2.0, the main lensreproduces the object at a virtual plane, and the optics of themicrolens array are selected in order to focus each microlens to thevirtual image plane and also generate focused copies of the virtualimage plane at the detector. The fundamental difference betweenplenoptic 1.0 and plenoptic 2.0 is that plenoptic 1.0 trades spatialresolution (i.e., fewer pixels image the scene) for angular resolution,while plenoptic 2.0 trades angular resolution (i.e., fewer syntheticperspectives and focused planes) for spatial resolution.

Other than a decrease in spatial resolution, plenoptic cameras haveseveral advantages over the conventional camera. For example, the imageof a scene can be refocused after the picture is taken (e.g., as shownin FIGS. 3A and 3B). The image can be focused to different depths, andalso the viewpoint can be modified. One classic photography trick toenhance a picture dynamic range is to capture the scene with twodifferent exposures (e.g., 100% and 20% exposures). Then, the shortexposure image is used to correct over-saturated objects in the fullexposure image. For conventional photography, the technique requires twoseparate exposures in time. For a plenoptic camera, a checkerboardfilter mask is placed at the main lens or at the microlens array inorder to capture the scene at two different illumination exposures witha single exposure. In this way, the dynamic range enhancement can beapplied to moving objects. A similar filter mask with multiple differentband-pass regions can be used to capture multispectral images with asingle exposure.

A very useful feature of plenoptic cameras is the ability to measuredepth from the light field. A light field contains information about thedirection of rays reflecting from the object in a scene. This directioninformation allows the reconstruction of the scene from differentperspectives. Therefore, computer vision techniques like depth fromstereo can be used to estimate depth and three-dimensional shape of anobject. From depth estimation, one can generate images where the extentof the scene is in focus. Objects in a stack of images are segmentedbased on their depth, and non-overlapping regions of focused objects (orportions thereof) at different depths are stitched together in order togenerate a fully in-focus image with a large depth of field.

Example 31 Example Application to Iris Recognition

The human iris is one of the most reliable biometrics, given its highdegree of entropy per unit area. Moreover, this biometric signature isless intrusive, hard to change, and virtually constant as the personages. However, the fact only holds for high quality images of frontalirises or ideal irises. The quality of the iris image is a function offocus blur, occlusions, lighting, the number of sensor pixels across theiris, and other factors. A low quality iris is considered a non-idealiris. The recognition of non-ideal irises is a field of extensiveresearch, but no comprehensive solution has been engineered yet,particularly for off-axis irises.

A traditional camera has access to the light field of a scene, but ofthe acquired two-dimensional image is a reduction of the largestfourth-dimensional light field space. By translating the position of thecamera optics, the camera can focus at different depths of the imagedobject. However, the operator can only pick a particular focus depthwhen acquiring an image. In particular to iris imaging, the fixed focallength of the optics found in most current iris scanners makes thosesystems prone to capture non-ideal images due to the shallow depth offield. A plenoptic camera does not have such limitations. From the lightfield, several images focused at different object's depths can begenerated synthetically (i.e., in the computer or processing chip afterthe image is captured by the camera).

FIG. 14 is an illustration of how the light field can be sampled with aplenoptic camera. For simplification, the camera design is based on aplenoptic 1.0 scheme (i.e., the main lens focuses light rays directly atthe microlens array), reduced to a two-dimensional drawing and with onlytwo pixels to sample angular information. One can extend the design tothree-dimensional scenarios and with several microlenses and angularpixels.

As shown in FIG. 14, the pixels behind a microlens correspond to aregion in the main lens. The main lens focuses photons from points inthe object (e.g., eye) to the corresponding microlens and is done in thetraditional camera. Then, given the angle of the photon ray, themicrolens will focus the photon ray to the corresponding angular pixel.In the illustration, photon rays with angles greater than zero gothrough the main lens region “u” and are binned in the microlens pixels“u.” Otherwise, the rays correspond to the “v” region and pixels for themain lens and microlenses respectively. Rays hitting a particularmicrolens correspond to a point in the object space while those passingthrough a main lens region correspond to a particular ray angle andtheir storage index is known.

Note that the above description reduces image reconstruction to theprocess of finding the line/point intersections of rays passing througha main lens region and microlens that correspond to a particular focusplane.

In order to focus to a given point, one can define a synthetic apertureor pupil as shown in FIG. 14. The pupil is centered at any position mbetween the main lens and the microlenses. Each different pupil positioncorresponds to a different focus plane and/or perspective at the objectspace. Rays intersecting the point m as shown in FIG. 14 are used toreconstruct an image of the object at a certain focus depth. Positioningthe pupil at extreme positions as too close to the microlenses or themain lens can limit the number of ray samples for such an extremeposition, which may produce low quality reconstructions. Some of therays may not exactly intersect the center of the pupil; consequently,interpolation techniques may be applied to determine the proper weightof rays passing through the synthetic pupil.

Example 32 Example System Implementing Reconstruction Via Eye Model

FIG. 15 is a block diagram of an example system 1500 implementingfrontal view reconstruction via an eye model. In the example, thefrontal view reconstruction engine 1550 accepts an off-angle image 1510as input and outputs the reconstructed image 1580.

The frontal view reconstruction engine 1550 can comprise a ray-tracingengine 1555 and an eye model 1560 that can be used to generate asynthetic eye 1557. A frontal view of the synthetic eye can then begenerated for use as the reconstructed image 1580. Additional imageprocessing and filtering can be performed.

Example 33 Example Method Implementing Reconstruction Via Eye Model

FIG. 16 is a flowchart of an example method 1600 of implementing frontalview reconstruction via an eye model and can be implemented, forexample, via the system shown in FIG. 15.

At 1610, an off-angle image (e.g., depicting an iris) is received.

At 1620, a reconstructed synthetic eye is constructed from an off-angleimage and eye model via ray tracing. Ray-tracing techniques can be usedto generate a synthetic eye (e.g., the iris) on which additionalprocessing can be performed. Essentially, ray tracing writes thesynthetic iris appearance to a representation of a synthetic iris inappropriate locations mimicking a physical manifestation of the iris.Alternatively, a mapping between points can be determined without havingactual iris data.

At 1630, a reconstructed image is constructed from the reconstructedsynthetic eye and eye model via ray tracing. Again, ray tracing can beused, but a frontal view can be generated. Essentially, the syntheticeye is viewed from the front (e.g., by a synthetic camera).

Example 34 Example Gaze Information

In any of the examples herein, gaze information can be used for avariety of purposes. Such information can include the distance to theeye (e.g., from the camera, whether actual or synthetic), gaze anglecombination (e.g., horizontal, vertical, or both) with respect to theoptical axis, and the like. Other information, such as focal length,sensor characteristics, and the like can be included in the analysis. Insome cases, the information can be determined from an image, or theinformation may be known, included as metadata, or the like.

To determine gaze angle, eccentricity of the iris or pupil can be used.

Example 35 Example System Constructing Reconstructed Synthetic Eye

FIG. 17 is a block diagram of an example system 1700 constructing areconstructed synthetic eye from an off-angle image. The system 1700operates to generate a synthetic eye 1757 that can be used inconjunction with other systems to provide a complete solution to frontalview reconstruction.

In the example, the frontal view reconstruction engine 1750 receives anoff-angle image 1710 and generates a synthetic eye 1757 (e.g., iris) viathe ray-tracing engine 1755. As described herein, the synthetic eye 1757can then be used to generate a reconstructed frontal view of the irisdepicted in the off-angle image 1710. In practice, the systems can becombined into a single engine.

The ray-tracing engine 1755 can perform ray tracing as described hereinwith reference to an eye model 1760 and gaze information 1745 asdetermined by the gaze analyzer 1740 to generate the synthetic eye 1757.Other information can be obtained from other sources.

Example 36 Example Method of Constructing Synthetic Eye

FIG. 18 is a flowchart of an example method 1800 of constructing asynthetic eye from an off-angle image and can be implemented, forexample, in the system shown in FIG. 17.

At 1810, an off-angle image depicting an iris is received.

At 1820 the gaze of the eye is determined.

At 1830, a reconstructed synthetic eye (e.g., iris) is constructed basedon the gaze of the eye and an eye model via ray tracing as describedherein.

Example 37 Example System Reconstructing Image from Synthetic Eye

FIG. 19 is a block diagram of an example system 1900 reconstructing animage from a synthetic eye. In the example, the synthetic eye 1957(e.g., iris) is received as input by a ray-tracing engine 1955, which isable to output a reconstructed image 1980 from the synthetic eye 1957and model corneal refraction as described herein.

The eye model 1960 can include information about the cornea, the shapeof the eye (e.g., aspherical), and the like. The gaze information 1945may be simplified because the gaze angle is desired to be 0 for bothhorizontal and vertical angles. Other information, such as cameralocation, focal length, sensor size, and the like can be incorporated.

Due to the limbus effect, some information that is available in thesynthetic iris may be occluded by the limbus in a frontal view. If so,it is not depicted in the reconstructed image 1980.

Also as described herein, some information may not have been available(e.g., portions of the iris are unviewable) in the off-angle image dueto limbus occlusion, so the reconstructed frontal image 1980 may bemissing such information. The information can be designated as to bemasked when performing recognition.

Example 38 Example Method of Reconstructing Image from Synthetic Eye

An example method reconstructing a frontal image from a synthetic eyecan be implemented, for example, in the system shown in FIG. 10.

A synthetic eye (e.g., iris) is received. The synthetic eye canrepresent the texture of the iris in two-dimensional orthree-dimensional space.

A re-projected image of the iris is constructed based on a frontal gazeand the eye model via ray tracing as described herein.

The reconstructed image is output. The image can then be used for imagerecognition purposes or to construct a precomputed transform asdescribed herein.

Example 39 Example Ray Tracing

FIG. 20 is a block diagram showing a ray trace model for reconstructinga frontal view. As described herein, the model can be used to constructa synthetic eye and then reconstruct a frontal view via the syntheticeye.

Example 40 Example Limbus Effects

FIG. 21 is a block diagram showing effects of the limbus. The irisvisible region changes with gaze. Because of the off-angle gaze, someportions of the limbus (e.g., corresponding to additional imageinformation 2120) are visible in the off-angle gaze that would not bevisible in a frontal view. As described herein, such information isdiscarded (e.g., not included) when reconstructing the frontal view.

Similarly, because of the off-angle gaze, some portions of the limbus2130 that would be visible in a frontal view are occluded. Suchinformation can be masked from consideration (e.g., in the probe and thegallery image) to prevent it from disrupting the recognition process.

Example 41 Example Limbus Effects on Reconstructed Frontal Image

FIG. 22 is a block diagram showing effect of the limbus on areconstructed frontal image of an iris. The image is not to scale. Aphysical location of the limbus (e.g., within the eye) can be modeledduring the reconstruction process to determine the effect of the limbuson the reconstructed frontal image.

As a result, in any of the examples herein, reconstructing the frontalview 2210 can comprise removing a portion 2220 of the off-angle irisimage occluded by the limbus due to the frontal view being viewedfrontally.

As another result, in any of the examples herein, when reconstructing afrontal view, a portion of the frontal view of the iris can be maskedfrom consideration during iris recognition (e.g., due to limbusocclusion). The limbus occlusion causes certain portions of the iris2230 to be unavailable for reconstruction. Accordingly, the portions ofthe iris that were occluded by the limbus in the off-angle iris image(e.g., as indicated by the eye model) can be so masked. Because suchinformation is not available for reconstruction, masking it fromconsideration during iris recognition can result in better recognitionperformance. Masking can prevent the portion of the gallery image thatcorresponds to the missing portion of the probe image from beingconsidered, which would otherwise result in mismatch of the imageportion that is being masked.

Also, when segmentation is performed on the iris, such segmentation canbe based on modeled occlusion by the limbus, resulting in more accuratesegmentation. Thus, iris and non-iris image data can be properlyseparated. Subsequently, when the image of the iris is unwrapped, theimproved segmentation can result in superior unwrapped image results,which are ultimately submitted for recognition by iris recognitionlogic.

Example 42 Example Masking of Image

As described herein, when a frontal view is reconstructed, someinformation (e.g., portions of the iris) may be not be available becausesome portions of the iris may not have been viewable due to the gazeangle and occlusion by the limbus. In such a case, the areas of theimage can be masked from consideration during the recognition process.

A recognizer may accept parameters (e.g., via an API or other mechanism)to indicate which portions of the image are not to be considered duringrecognition. Consequently, the masked portions can be disregarded duringrecognition (e.g., comparison with gallery images).

Example 43 Example Ray-Tracing Implementation: Limbus Effect

Accurate off-axis iris recognition requires understanding the role ofthe limbus effect. As shown in FIGS. 23A-B, the limbus is asemi-transparent member of the eye that changes from opaque at theboundary with the sclera to totally transparent at the boundary with thecornea. An assessment of Optical Coherence Tomography (OCT) images, asshown in FIG. 23B, indicates that the limbus significantly occludesregions of the iris for off-axis images beyond 25°. The phenomena can becalled the ‘limbus effect’.

The entire iris is never truly visible because at any angle, evenfrontal, some of the iris is occluded by the limbus. When viewing theiris from the same angle, such as frontal, the same portion of the irisis always visible resulting in no depreciation in iris recognitionperformance. However, off-angle iris imaging can result in a significantdecrease in recognition performance due to what is essentially asegmentation problem.

FIG. 24A is a rendering of an example at 0 degrees. The region betweendashed lines is occluded by the limbus. Unwrapping results for the eyein FIG. 24A are shown in FIG. 24B overlooking the limbus effect, andFIG. 24C takes the limbus effect into account.

Conventional iris segmentation practices assume that the iris is notoccluded by the limbus. Therefore, such solutions incorrectly assumethat the iris starts at the fuzzy boundary shared by the cornea andlimbus. The incorrect segmentation will produce an unwrapped iris withsome regions of the texture stretched (See FIG. 24B). On the other hand,when the limbus effect is taken into account, the unwrapped iris is atthe correct scale (See FIG. 24C), the occluded areas can be removed fromthe iris code, and a similarity can be better estimated. The limbuseffect causes a significant portion of the degradation of traditionaloff-axis iris recognition performance.

Example 44 Example Embodiment

An example embodiment can be a system comprising one or more hardwareprocessing units; non-transitory computer-readable memory coupled to theone or more hardware processing units; and a fully focused iris imagestitching engine, wherein the fully focused iris image stitching engineis configured to accept a plurality of reconstructed images at differentsynthetic focus depths of an iris with an off-angle gaze and output afully focused image of the iris, wherein the fully focused iris imagestitching engine stitches together different in-focus regions of theiris from the plurality of reconstructed images.

Example 45 Example Applications

The technologies herein can be applied to any of a wide variety ofapplications in which iris recognition can be used, including access toa secure facility or checkpoint, access to the home, access to personalinformation, identification of a person of interest, helping lawenforcement identify individuals, identify clients to offer products,and the like.

Example 46 Example Computing Systems

FIG. 25 illustrates a generalized example of a suitable computing system2500 in which several of the described innovations may be implemented.The computing system 2500 is not intended to suggest any limitation asto scope of use or functionality, as the innovations may be implementedin diverse general-purpose or special-purpose computing systems.

The technologies can also be implemented in specialized hardware (e.g.,an iris-recognition appliance) that can contain additional elements(e.g., a high definition camera or the like).

With reference to FIG. 25, the computing system 2500 includes one ormore processing units 2510, 2515 and memory 2520, 2525. In FIG. 25, thisbasic configuration 2530 is included within a dashed line. Theprocessing units 2510, 2515 execute computer-executable instructions. Aprocessing unit can be a general-purpose central processing unit (CPU),processor in an application-specific integrated circuit (ASIC) or anyother type of processor. In a multi-processing system, multipleprocessing units execute computer-executable instructions to increaseprocessing power. For example, FIG. 25 shows a central processing unit2510 as well as a graphics processing unit or co-processing unit 2515.The tangible memory 2520, 2525 may be volatile memory (e.g., registers,cache, RAM), non-volatile memory (e.g., ROM, EEPROM, flash memory,etc.), or some combination of the two, accessible by the processingunit(s). The memory 2520, 2525 stores software 2580 implementing one ormore innovations described herein, in the form of computer-executableinstructions suitable for execution by the processing unit(s).

A computing system may have additional features. For example, thecomputing system 2500 includes storage 2540, one or more input devices2550, one or more output devices 2560, and one or more communicationconnections 2570. An interconnection mechanism (not shown) such as abus, controller, or network interconnects the components of thecomputing system 2500. Typically, operating system software (not shown)provides an operating environment for other software executing in thecomputing system 2500, and coordinates activities of the components ofthe computing system 2500.

The tangible storage 2540 may be removable or non-removable, andincludes magnetic disks, magnetic tapes or cassettes, CD-ROMs, DVDs, orany other medium which can be used to store information in anon-transitory way and which can be accessed within the computing system2500. The storage 2540 stores instructions for the software 2580implementing one or more innovations described herein.

The input device(s) 2550 may be a touch input device such as a keyboard,mouse, pen, or trackball, a voice input device, a scanning device, oranother device that provides input to the computing system 2500. Forvideo encoding, the input device(s) 2550 may be a camera, video card, TVtuner card, or similar device that accepts video input in analog ordigital form, or a CD-ROM or CD-RW that reads video samples into thecomputing system 2500. The output device(s) 2560 may be a display,printer, speaker, CD-writer, or another device that provides output fromthe computing system 2500.

The communication connection(s) 2570 enable communication over acommunication medium to another computing entity. The communicationmedium conveys information such as computer-executable instructions,audio or video input or output, or other data in a modulated datasignal. A modulated data signal is a signal that has one or more of itscharacteristics set or changed in such a manner as to encode informationin the signal. By way of example, and not limitation, communicationmedia can use an electrical, optical, RF, or other carrier.

The innovations can be described in the general context ofcomputer-executable instructions, such as those included in programmodules, being executed in a computing system on a target real orvirtual processor. Generally, program modules include routines,programs, libraries, objects, classes, components, data structures, etc.that perform particular tasks or implement particular abstract datatypes. The functionality of the program modules may be combined or splitbetween program modules as desired in various embodiments.Computer-executable instructions for program modules may be executedwithin a local or distributed computing system.

For the sake of presentation, the detailed description uses terms like“determine” and “use” to describe computer operations in a computingsystem. These terms are high-level abstractions for operations performedby a computer, and should not be confused with acts performed by a humanbeing. The actual computer operations corresponding to these terms varydepending on implementation.

Example 47 Example Cloud-Supported Environment

In example environment 2600, the cloud 2610 provides services forconnected devices 2630, 2640, 2650 with a variety of screencapabilities. Connected device 2630 represents a device with a computerscreen 2635 (e.g., a mid-size screen). For example, connected device2630 could be a personal computer such as desktop computer, laptop,notebook, netbook, or the like. Connected device 2640 represents adevice with a mobile device screen 2645 (e.g., a small-size screen). Forexample, connected device 2640 could be a mobile phone, smart phone,personal digital assistant, tablet computer, and the like. Connecteddevice 2650 represents a device with a large screen 2655. For example,connected device 2650 could be a television screen (e.g., a smarttelevision) or another device connected to a television (e.g., a set-topbox or gaming console) or the like. One or more of the connected devices2630, 2640, 2650 can include touch screen capabilities. Touchscreens canaccept input in different ways. For example, capacitive touchscreensdetect touch input when an object (e.g., a fingertip or stylus) distortsor interrupts an electrical current running across the surface. Asanother example, touchscreens can use optical sensors to detect touchinput when beams from the optical sensors are interrupted. Physicalcontact with the surface of the screen is not necessary for input to bedetected by some touchscreens. Devices without screen capabilities alsocan be used in example environment 2600. For example, the cloud 2610 canprovide services for one or more computers (e.g., server computers)without displays.

Services can be provided by the cloud 2610 through service providers2620, or through other providers of online services (not depicted). Forexample, cloud services can be customized to the screen size, displaycapability, and/or touch screen capability of a particular connecteddevice (e.g., connected devices 2630, 2640, 2650).

In example environment 2600, the cloud 2610 provides the technologiesand solutions described herein to the various connected devices 2630,2640, 2650 using, at least in part, the service providers 2620. Forexample, the service providers 2620 can provide a centralized solutionfor various cloud-based services. The service providers 2620 can manageservice subscriptions for users and/or devices (e.g., for the connecteddevices 2630, 2640, 2650 and/or their respective users).

Example 48 Computer-Readable Media

Any of the computer-readable media herein can be non-transitory (e.g.,volatile memory such as DRAM or SRAM, nonvolatile memory such asmagnetic storage, optical storage, flash memory, solid state drives, orthe like) and/or tangible. Any of the storing actions described hereincan be implemented by storing in one or more computer-readable media(e.g., computer-readable storage media or other tangible media). Any ofthe things (e.g., data created and used during implementation) describedas stored can be stored in one or more computer-readable media (e.g.,computer-readable storage media or other tangible media).Computer-readable media can be limited to implementations not consistingof a signal.

Any of the methods described herein can be implemented bycomputer-executable instructions in (e.g., stored on, encoded on, or thelike) one or more computer-readable media (e.g., computer-readablestorage media or other tangible media) or one or more computer-readablestorage devices (e.g., memory, magnetic storage, optical storage, or thelike). Such instructions can cause a computing device to perform themethod. The technologies described herein can be implemented in avariety of programming languages.

ALTERNATIVES

The technologies from any example can be combined with the technologiesdescribed in any one or more of the other examples. In view of the manypossible embodiments to which the principles of the disclosed technologymay be applied, it should be recognized that the illustrated embodimentsare examples of the disclosed technology and should not be taken as alimitation on the scope of the disclosed technology. Rather, the scopeof the disclosed technology includes what is covered by the followingclaims. We therefore claim as our invention all that comes within thescope and spirit of the claims.

1. A method implemented at least in part by a computing system, themethod comprising: receiving a plenoptic off-angle iris image depictingan iris with an off-angle gaze; from the plenoptic off-angle iris imagedepicting an iris with an off-angle gaze, creating a plurality ofreconstructed images at different synthetic focal depths, wherein theplurality of reconstructed images comprise different in-focus regions ofthe iris; and stitching together the different in-focus regions of theiris from the plurality of reconstructed images, wherein the stitchinggenerates a fully focused image of the iris.
 2. One or morecomputer-readable media having encoded thereon computer-executableinstructions causing a computing system to perform a method comprising:receiving a plenoptic off-angle iris image depicting an iris with anoff-angle gaze; from the plenoptic off-angle iris image depicting aniris with an off-angle gaze, creating a plurality of reconstructedimages at different synthetic focal depths, wherein the plurality ofreconstructed images comprise different in-focus regions of the iris;and stitching together the different in-focus regions of the iris fromthe plurality of reconstructed images, wherein the stitching generates afully focused image of the iris.
 3. The method of claim 1 furthercomprising: submitting the fully focused image of the iris to an irisrecognizer for iris recognition processing.
 4. The method of claim 1further comprising: dividing a particular reconstructed image into aplurality of regions; determining that at least one of the plurality ofregions is in focus; and using the at least one in-focus region for thestitching together.
 5. The method of claim 1 further comprising:dividing the plenoptic off-angle iris image into a plurality of overallregions; and identifying respective of the reconstructed images havingin-focus regions corresponding to the overall regions; wherein thestitching together stitches together the in-focus regions correspondingto the overall regions.
 6. The method of claim 1 further comprising:identifying the different in-focus regions in respective of thereconstructed images.
 7. The method of claim 6 wherein the identifyingcomprises analyzing entropy.
 8. The method of claim 6 wherein theidentifying comprises analyzing contrast between neighboring pixels. 9.A method implemented at least in part by a computing system, the methodcomprising: receiving a plenoptic iris image depicting an iris; from theplenoptic iris image depicting an iris, determining a three-dimensionalshape of the iris; storing the three-dimensional shape of the iris; andapplying the three-dimensional shape of the iris as part of irisrecognition processing.
 10. The method of claim 9 wherein: determining athree-dimensional shape of the iris comprises: computing a depth map ofthe plenoptic iris image; segmenting the iris as depicted in theplenoptic iris image; and registering the segmented iris to the depthmap.
 11. The method of claim 9 wherein: applying the three-dimensionalshape of the iris as part of iris recognition processing comprises:constructing a personalized eye model based on the three-dimensionalshape of the iris; and performing iris recognition via the personalizedeye model.
 12. The method of claim 9 wherein: applying thethree-dimensional shape of the iris as part of iris recognitionprocessing comprises: constructing a personalized eye model based on thethree-dimensional shape of the iris; via the personalized eye model,reconstructing a frontal view of an iris depicted in an off-angle irisimage; and performing iris recognition with the reconstructed frontalview.
 13. The method of claim 9 further comprising: from the plenopticiris image, determining a three-dimensional shape of a limbus depictedin the plenoptic iris image; storing the three-dimensional shape of thelimbus; and applying the three-dimensional shape of the limbus duringiris recognition processing.
 14. The method of claim 13 furthercomprising: performing iris recognition, wherein the iris recognitionaccounts for the three-dimensional shape of the limbus.
 15. The methodof claim 14 wherein: the plenoptic iris image depicts an iris with anoff-angle gaze; wherein the method further comprises: based on thethree-dimensional shape of the limbus, determining a portion of the iristhat is occluded by the limbus in an on-angle gaze; and during irisrecognition, removing the occluded portion of the iris fromconsideration.
 16. The method of claim 9 further comprising: storing athree-dimensional position of the limbus.
 17. The method of claim 16wherein: the plenoptic iris image depicts an iris with an off-anglegaze; wherein the method further comprises: based on thethree-dimensional position of the limbus, determining a portion of theiris that is occluded by the limbus in an on-angle gaze; and during irisrecognition, removing the occluded portion of the iris fromconsideration.
 18. The method of claim 9 further comprising: based onthe three-dimensional shape of the iris, determining that no obfuscatingcontact lens is present.
 19. (canceled)
 20. (canceled)